Good news! Jim (creator of the fantastic
PocketShield and Volumex applications) pointed me in the right direction. The reversed engineered APIs that are already wrapped and ready to use in Visual Studio with C# examples are publicly available here:
http://sensorapi.codeplex.com/
They even have sample code there. Just download the solution, compile in VS, drop the exes and dlls on the PT2 and the samples work great! The NavSensor does not work since it is designed for the round center button that TP1 had for example; but G-sensor, light sensor, and stilus out APIs work great. I don't think there is anything for the proximity sensor or at least I couldn't find anything else.
There are more samples/discussions on xda and on
http://www.basic4ppc.com/forum/index.php sites.
Cheers.
EDIT: Oh, and as one example of using a G-sensor API - this
lightsaber application is hilarious and runs great on TP2!
